if not which("ffmpeg"):
        print "ffmpeg: Executable not found on machine."
        raise Exception("Dependency not found: ffmpeg")

As for why the error is reported, the which command detects whether there is a correct output after inputting the which parameter on the command line, here to check whether ffmpeg is installed successfully.

However, here seems to only check ffmpeg in the python root directory. If there is no ffmpeg in the python root directory, an error will be reported. As for why, I don’t want to toss it anymore.

Another problem is that if you copy ffmpeg to the python root directory before, you must delete it. Otherwise, after commenting out raise, another error will be reported. It seems that he would prefer to use ffmpeg in the python root directory.

Pro-test is available, as shown in the figure